Comedian Jay Leno during an interview with guest host David Letterman on The Tonight Show on July 4, 1979.

Photo: NBC, NBC Via Getty Images

Comedian Jay Leno during an interview with guest host David...

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Headshot of David Letterman for the show, "Mary," in 1978.

Photo: CBS Photo Archive, CBS Via Getty Images

Headshot of David Letterman for the show, "Mary," in 1978.

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Actress Betty White and guest host David Letterman on The Tonight Show in 1979.

Photo: NBC, NBC Via Getty Images

Actress Betty White and guest host David Letterman on The Tonight...

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Jerry Garcia, Bob Weir, and David Letterman in 1982.

Photo: Time & Life Pictures, Time Life Pictures/Getty Images

Jerry Garcia, Bob Weir, and David Letterman in 1982.

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David Letterman in 1979.

Photo: NBC, NBC Via Getty Images

David Letterman in 1979.

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David Letterman during The 37th Annual Emmy Awards at Pasadena Civic Auditorium in Pasadena, Calif., 1985.

Photo: Ron Galella, WireImage

David Letterman during The 37th Annual Emmy Awards at Pasadena...

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David Letterman as Ellsworth in a 1979 episode of "Mork and Mindy."

Photo: CBS Photo Archive, CBS Via Getty Images

David Letterman as Ellsworth in a 1979 episode of "Mork and Mindy."

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FILE - In this April 23, 2012 file photo provided by CBS, host David Letterman appears during a taping of his show “Late Show with David Letterman, in New York. Letterman says he plans to retire next year as host of “Late Show.” During a taping of his show Thursday, April 3, 2014, Letterman said he has informed his CBS bosses that he will step down in 2015, when his current contract expires. He told his audience he expects his departure will be “at least a year or so” from now. MANDATORY CREDIT; NO ARCHIVE; ; NORTH AMERICAN USE ONLY

Photo: John Paul Filo, AP

FILE - In this April 23, 2012 file photo provided by CBS, host...

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FILE - In this June 21, 2012 file photo provided by CBS, host David Letterman appears at a taping of his shows"Late Show with David Letterman" in New York. During a taping of his show Thursday, April 3, 2014, Letterman said he has informed his CBS bosses that he will step down in 2015, when his current contract expires. He told his audience he expects his departure will be “at least a year or so” from now. MANDATORY CREDIT

FILE - In this Sept. 24, 2013 file photo provided by CBS, Cher embraces host David Letterman after she performed a song off her new album, on “Late Show with David Letterman,” in New York. During a taping of his show Thursday, April 3, 2014, Letterman said he has informed his CBS bosses that he will step down in 2015, when his current contract expires. He told his audience he expects his departure will be “at least a year or so” from now. MANDATORY CREDIT; ; NO ARCHIVE; FOR NORTH AMERICAN USE ONLY)

Photo: Jeffrey R. Staab, AP

FILE - In this Sept. 24, 2013 file photo provided by CBS, Cher...

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LOS ANGELES, CA - MARCH 27: US television personality David Letterman delivers his opening monologue as he hosts the 67th annual Academy Awards in Los Angeles 27 March. Letterman, who stars in the "Late Show with David Letterman" on CBS-TV, is the third Academy Awards host in as many years. AFP PHOTO (Photo credit should read DON EMMERT/AFP/Getty Images)

Photo: DON EMMERT, AFP/Getty Images

LOS ANGELES, CA - MARCH 27: US television personality David...

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Todd Oliver & Friends features ventriloquist/comedian Todd Oliver and his pets. The show will be at The Palace Danbury (Conn.) on Saturday, March 15, 2014. Oliver was a semi-finalist on America's Got Talent and has appeared on many other television programs, from Late Night with David Letterman to The Tonight Show with Jay Leno.

Photo: Contributed Photo

Todd Oliver & Friends features ventriloquist/comedian Todd...

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In this Feb. 4, 2014 photo provided by CBS, surviving Beatles Paul McCartney, left and Ringo Starr, center, pose for a photo with talk show host David Letterman in the Ed Sullivan Theater, in New York. Letterman's special interview with them will be featured in "The Beatles: The Night That Changed America - A Grammy Salute," that will air Sunday, Feb. 9 on CBS. (AP Photo/CBS, Jeffrey R. Staab)

On a prior visit with David Letterman, Eva Longoria flashed plenty of leg and cleavage in a sexy blazer and shorts suit.

On a prior visit with David Letterman, Eva Longoria flashed plenty...

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David Letterman 'Late Night': $20 million per year
LATE NIGHT

Photo: HEATHER WINES, CBS

David Letterman 'Late Night': $20 million per year
LATE NIGHT

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Talk show host David Letterman appears in a rare and candid interview, talking to Oprah Winfrey, at 9/8c Sunday, Jan. 6, 2013, on the Oprah Winfrey Network, at his alma mater, Ball State University. Here's a look at Letterman over the years:

Photo: 2012 Getty Images

Talk show host David Letterman appears in a rare and candid...

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1982: David Letterman, warms up his NBC studio audience prior to the taping of his popular television show at Rockefeller Center. Getty Images

Photo: 1986 George Rose

1982: David Letterman, warms up his NBC studio audience prior to...

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1979: American television host David Letterman poses with Carol Morra during a party at the Hollywood Palladium. Getty Images

Photo: 2003 Getty Images

1979: American television host David Letterman poses with Carol...

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circa 1982: The David Letterman Show - Season 1. Host David Letterman with guests. Getty Images

Photo: 2012 NBCUniversal Media, LLC

circa 1982: The David Letterman Show - Season 1. Host David...

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1982: Host David Letterman. Getty Images

Photo: 2012 NBCUniversal Media, LLC

1982: Host David Letterman. Getty Images

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1982: Comedian and late-night talk show host David Letterman poses in his dressing room with girlfriend Merrill Markoe during a photo portrait session in New York City, New York. Markoe was also a writer for the 'Late Night With David Letterman.' Getty Images

Photo: 1982 George Rose

1982: Comedian and late-night talk show host David Letterman poses...

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1982: American talk show host David Letterman stands with his hands in his pockets as he gives a monologue at the beginning of a broadcast, New York. Getty Images

Photo: 2007 Getty Images

1982: American talk show host David Letterman stands with his hands...

1985: American comedian and talk show host David Letterman smokes a cigar and smiles while holding his trophy for Outstanding Writing - Variety or Music Program at the 37th Annual Emmy Awards. Getty Images

1985: American comedian and talk show host David Letterman smokes a...

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1986: David Letterman sits at his desk on the television series 'Late Night with David Letterman,' New York, New York. Getty Images

1986: David Letterman sits at his desk on the television series...

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1985: David Letterman, wearing a baseball cap from the television series, 'Miami Vice,' biting a cigar. Getty Images

NEW YORK (AP) — David Letterman is retiring next year as host of "Late Show."

During a taping of Thursday's show, Letterman said he has informed CBS that he will step down in 2015, when his current contract expires.

He specified no end date, telling his audience he expects his exit will be in "at least a year or so, but sometime in the not too distant future — 2015, for the love of God — (band leader) Paul (Shaffer) and I will be wrapping things up."

Referring to CBS chairman Leslie Moonves as "the man who owns this network," Letterman said: "I phoned him just before the program, and I said 'Leslie, it's been great, you've been great, and the network has been great, but I'm retiring.'"

Video: Emanuel talks Syria, Chicago homicides on Letterman

Media: Houston Chronicle
Chicago Mayor Rahm Emanuel made an appearance on "The Late Show with David Letterman" on Monday to discuss some of the nation's top issues. (Posted on: September 10, 2013)

Along with his network, Letterman thanked "all of the people who have worked here, all of the people in the theater, all the people on the staff, everybody at home, thank you very much.

"What this means now," he cracked, "is that Paul and I can be married."

Letterman, who turns 67 next week, has the longest tenure of any late-night talk show host in U.S. television history, already marking 32 years since he created "Late Night" at NBC in 1982.

After losing the "Tonight Show" throne to rival candidate Jay Leno in 1993, he jumped to CBS to start "Late Show."

"For 21 years, David Letterman has graced our network's air in late night with wit, gravitas and brilliance unique in the history of our medium," said Moonves. "It's going to be tough to say goodbye. Fortunately, we won't have to do that for another year or so. Until then, we look forward to celebrating Dave's remarkable show and incredible talents."

Leno retired from "The Tonight Show" earlier this year, making way for "Late Night" host Jimmy Fallon to take over that NBC institution.

Leno held the ratings leadership for most of his two-decade duel with Letterman, but Dave remained the overwhelming critical favorite, pushing forward in a "Tonight Show" tradition forged by Johnny Carson and, before him, Jack Paar and Steve Allen.

"Late Show" won a prime-time Emmy in 1994. Letterman earned a Peabody Award in 1992 and was a Kennedy Center Honoree in 2012.

In an interview with Howard Stern in January, Letterman said that Leno's departure would have no impact on how much longer he might stay as host of "Late Show."

"I would do it forever if it were up to me," said Letterman, before adding a wry aside: "Sometimes, it isn't up to me."

With the late-night dust now settling at NBC, Who Replaces Letterman becomes the new guessing game. In the wings as a likely heir: Craig Ferguson, host of "The Late Late Show." It has followed Letterman, who produces it, since 2005.

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EDITOR'S NOTE — Frazier Moore is a national television columnist for The Associated Press. He can be reached at fmoore@ap.org and at http://www.twitter.com/tvfrazier